21378806 has 8 divisors (see below), whose sum is σ = 32092200. Its totient is φ = 10681408.

The previous prime is 21378767. The next prime is 21378817. The reversal of 21378806 is 60887312.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-3 number, since 3×21378806³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 245 + ... + 6543.

It is an arithmetic number, because the mean of its divisors is an integer number (4011525).

Almost surely, 2^21378806 is an apocalyptic number.

21378806 is a deficient number, since it is larger than the sum of its proper divisors (10713394).

21378806 is a wasteful number, since it uses less digits than its factorization.

21378806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7998.

The product of its (nonzero) digits is 16128, while the sum is 35.

The square root of 21378806 is about 4623.7220937249. The cubic root of 21378806 is about 277.5414260585.

The spelling of 21378806 in words is "twenty-one million, three hundred seventy-eight thousand, eight hundred six".